"Volatile" is one of the words that probably best describes the race for the Republican presidential nomination and a new CBS News poll captures that flux. The national poll indicates a three-way tie, showing Herman Cain at 18 percent and Mitt Romney and Newt Gingrich at 15 percent each.

That's essentially a tie since the margin of error is plus or minus three percentage points.

Perhaps it was only a matter of time before Gingrich rose to the top tier since every Republican candidate not named Romney has had his or her ascent in the polls often to fall back to the second tier.

The poll also indicates there's a very strong, damn-the-torpedoes-full-speed-ahead aspect in the Republican primary electorate as six in ten GOP primary voters say the sexual-harassment charges against Cain, the former pizza company executive, won't affect their vote.

Even so, the poll suggests that the charges have cut significantly into Cain's support with Republican women. His backing from that segment of voters has about halved from October, dropping to 15 percent of GOP woman from 28 percent last month.

Texas Gov. Rick Perry was in fourth place in the poll at 8 percent with the rest of the pack trailing him. The poll was taken from Sunday through Thursday so it presumably represents some of the impact from Perry's famous brain freeze at Wednesday night's Michigan debate.